My boat. The engine is an Olympia, manufactured in Vaasa, Finland, in the thirties. It's a single cylinder, sidevalve, four stroke, with 75mm bore and 110mm stroke. Peak power is at about 1000 rpm. The flywheel is very heavy. It has a handle which is used for crank starting. When the engine is running, the handle can be folded into a slot in the flywheel, by placing a shoe, or similar, close to the flywheel.
I have taken the engine completely apart to restore it. Spare parts are hard/impossible to find these days. So you have to make them yourself, or be creative with using parts from different engines. After a lot of searching, I found a piston with about the same dimensions as the stock piston. It's from a four cylinder Fiat from the seventies. The diameter is a few mm larger than stock, so the cylinder has been bored/honed to the right piston clearance. The piston top has been milled a few mm to get the right height/compression ratio. (About 6:1 in these engines). The connecting rod bronze bearing has been replaced and honed to fit the new piston pin. Shims in the crankshaft bearings has been changed to get the right bearing clearance. After the restoration, the engine is mechanically almost silent, and runs really smooth.
In the video, the engine stops just as I'm about to put it in gear, simply because I forgot to turn on the fuel valve...=)